This application claims the priority of German patent document 103 12 611.2, filed Mar. 21, 2003 (PCT International Application No. PCT/EP2004/000844, filed Jan. 30, 2004), the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for detecting an object in a detection field such as a motor vehicle detection field, by scanning the environment at predetermined angular increments.
German patent document DE 101 16 277 A1 discloses a device for detecting objects during operation of a motor vehicle, using a scanning detection means (in particular, a laser). Objects moving in relation to the vehicle are classified as regards their size, degree of reflection, speed and acceleration. The object is then identified (for example as a passenger vehicle, an HGV, a motorcycle, a bicycle or a pedestrian) using a subcombination of these evaluation variables.
German patent document DE 195 03 960 A1 also describes an object detection device for vehicles having a laser for emitting light and a device for receiving the light reflected by an object (laser scanner). The pulsed laser scans an environment using a predetermined number of increments, (for example 100), and the distance and speed of the object are determined in computing devices.
An obstacle identification device identifies the detected object on the basis of a distribution pattern of the light intensity received.
One disadvantage of the known radar devices is that the resolution of the laser scanners used is in many applications insufficient in the operating mode to be able to determine reliably the extent of an object to be detected.
One object of the present invention is to provide an improved method and apparatus for detecting an object in a motor vehicle environment, using a detection to scan the environment at predetermined angular increments.
This and other objects and advantages are achieved by the method and apparatus according to the invention, in which a reflection signal of an object is sensed at angles φi (i=1, 2, . . . , N). According to the invention, the angular increments are refined in the angular range between adjacent angles φi−1 and φi+1, as a function of the signal propagation times ti−1, ti and ti+1 of the reflection signals sensed at the angles φi−1, φi and φi+1. In order to detect the object in a motor vehicle environment, a detection unit is used which scans the environment at predetermined angular increments φi+1−φi. For many assisting and safety functions in the vehicle, knowledge of the precise dimensions of the objects located in the environment is indispensable. The method according to the invention ensures highly accurate determination of the dimensions of an object, (for example of a road user such as a vehicle), so that it is possible, for example, to assign it reliably to classes such as a pedestrian, bicycle, passenger car and HGV. Each of these classes is characterized by a specific acceleration behavior and movement pattern in the road traffic, so that a targeted and safe response to a current traffic situation is possible.
In one embodiment of the invention, if the absolute propagation time difference between the signal propagation times ti and ti−1 or ti and ti+1 (corresponding to sensing angles φi−1, φi and φi+1 of the reflection signals) exceeds a predetermined threshold value, at least one additional angle φz (z=1, 2, . . . , N) is sensed in the angular range between the angles φi−1 and φi or φi and φi+1. The predetermined threshold value for the absolute propagation time difference, it should be noted, is selected such that distinctive object features (for example lamps or a radiator grille in a vehicle) lead to measurable propagation time differences between adjacent reflection signals which lie below the predetermined threshold value for the absolute propagation time difference. Absolute propagation time differences between the signal propagation times ti and ti−1 or ti and ti+1 of adjacent reflection signals which exceed the predetermined threshold value, on the other hand, are a clear indication of obvious geometrical changes which can be associated, in particular, with object boundaries (for example the front, right-hand corner of the vehicle). The introduction of the additional angle φz to be sensed in the angular range between the angles φi−1 and φi or φi and φi+1 makes it possible for object boundaries to be determined substantially more accurately. The method, namely the introduction of further angles φiz additionally to be sensed, is continued until reliable detection of the size and classification of the object is ensured.
It is advantageous if the scanning takes place substantially horizontally, vertically and/or at a predetermined angle of inclination. With scanning which is carried out vertically or at a predetermined angle of inclination, the presence and the position of a curb can be detected. This prevents the vehicle from driving onto the curb or ensures that it does so in a manner which is not damaging to the tires. The position and alignment of the curb can also be used for the selection of a desired vehicle position in a parking space. In addition, the knowledge of the position of a curb can be used to find vacant parking spaces which are not provided or delimited by two vehicles but lie in front of, behind or next to a single vehicle and are delimited on the other side by a curb.
Another feature of the invention provides a device for detecting an object in a motor vehicle environment. According to the invention, the device can be used to set individually the angles φi to be scanned, so that a cost-effective sensor system is provided for detecting an object in a motor vehicle environment using one or a very limited number of measuring beams. The system is compact and can be positioned in many locations in the vehicle owing to its low installation depth.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.